1. Field of the invention
The present invention relates to an engine mount mounted to attenuate vibrations generated in an engine and to support the weight of the engine, and more particularly, to an engine mount having a self-variation property, which may vary vibration attenuation characteristics based on driving conditions even when a separate drive mechanism is not provided, thereby more efficiently attenuating vibrations within different frequency ranges.
2. Description of the Related Art
A general hydraulic mount (e.g., fluid-filled mount) is typically filled with a predetermined amount of hydraulic fluid to attenuate vibrations via the flow of the hydraulic fluid. The hydraulic mount entails higher production costs compared to a pneumatic mount, but is advantageous in terms of performance, and therefore the application range thereof is gradually increasing.
However, since vibrations generated in a vehicle may be transmitted through the road surface as well as through the engine and the characteristics of the generated vibrations may vary based on the conditions in which the vehicle is being driven, the use of a general hydraulic mount is limited to the simultaneous attenuation of vibrations having different frequency ranges. Therefore, an active amount has been developed based on the hydraulic mount. The active mount is capable of actively controlling vibration attenuation characteristics to more efficiently attenuate vibrations within a specific frequency range.
Particularly, the characteristics of the active mount may be controlled by switching the supply of current on or off. A volume-stiffness type active mount, in which the behavior of a vibrating membrane is controlled via the flow of hydraulic fluid, and a bypass-type active mount, in which a second flow path (e.g., for communication between an upper fluid chamber and a lower fluid chamber) is additionally formed and communication via the second flow path is controlled, are widely used.
Among these, describing the conventional bypass-type active mount with reference to FIG. 1, an elastic insulator 2 coupled to a core 1 is mounted in the upper region of a case, a diaphragm 4 is coupled to the lower end of the case, and a nozzle plate 3 is mounted between the insulator 2 and the diaphragm 4 to divide the interior space into an upper fluid chamber and a lower fluid chamber. The nozzle plate 3 has an annular flow path formed inside the periphery thereof to allow hydraulic fluid therein to flow between the upper fluid chamber and the lower fluid chamber. The flow of hydraulic fluid is induced as the inner volume of the upper fluid chamber increases or decreases when the insulator 2 coupled to the core 1 is elastically deformed by load and vibrations transmitted from an engine.
In addition, a second flow path is provided in the center of the nozzle plate 3 to enable additional communication between the upper fluid chamber and the lower fluid chamber in the vertical direction, and a rod 5 is disposed below the second flow path to connect the upper end to the diaphragm 4 to be movable vertically. A spring (not illustrated) is coupled to the rod 5 to provide the rod 5 with elastic force in the direction in which the rod 5 closes the second flow path (i.e. in the upward movement direction of the rod 5), and a coil 6 is disposed proximate to the rod 5. In addition, when power is applied to the coil 6, the rod 5 is moved downward by electromagnetic force, whereby additional communication between the upper fluid chamber and the lower fluid chamber is implemented via the second flow path.
However, since the active mount requires the additional mounting of a drive mechanism (e.g., including the rod, spring, coil and power application device) to the fluid-filled mount, consumption current is increased due to the addition of the drive mechanism, which may have a negative effect on fuel efficiency and may result in increased production costs and weight.